In the field of knitting machines or hosiery-making machines, needles are known which are provided in order to allow to transfer a stitch from one needle to an adjacent needle.
One of such needles is disclosed in International Publication WO-02/070799. Said needle has, along its shank, a contoured tab which extends laterally with respect to the shank of the needle and forms, on one side of the needle, a receptacle which can be crossed by the head of another needle arranged laterally to the needle being considered. When a needle of this kind is mounted on the knitting machine or hosiery-making machine, said receptacle is aligned with the adjacent needle. The needle being considered, or transferring needle, in a certain step of the knitting of an item is moved so that the loop of knitting or stitch, which is arranged on its shank, is arranged at this receptacle. The adjacent needle, or receiving needle, is then actuated so as to pass through the receptacle, crossing completely the loop of knitting with its head. The transferring needle and the receiving needle are then actuated so that the transferring needle releases the loop of knitting, which remains attached to the head of the receiving needle.
By means of this type of needle and by means of the method disclosed in International Publication WO-02/070799, to which reference is made for the sake of completeness, it is possible to transfer stitches from one needle to an adjacent needle in order to obtain particular patterns, in particular to obtain open-work effects.
This type of needle, due to the fact that it has a receptacle on a single side, allows to transfer the stitch only to one of the two needles which, in the machine, are arranged laterally to the transferring needle, i.e., to the needle that is aligned with the receptacle of the transferring needle.
The possibility to transfer the stitch only in one direction is not devoid from drawbacks.
By transferring the stitch only in one direction with plain jersey knitting, the knitting in fact tends to rotate in the direction of the transferred stitch. This tendency can be compensated partially by using yarns with specific twists, which however are difficult to obtain.
Moreover, the possibility to transfer the stitches only on one side of the needle constitutes a limitation to the patterns that can be produced.
Other methods which instead allow to transfer the stitch in one direction or the other, depending on the knitting requirements, are known in knitting machines and hosiery-making machines.
In two-bed rectilinear knitting machines, for example, the transfer of the stitch from one needle to the adjacent needle can be performed by transferring the stitch from a needle of one bed to a needle of the other bed, moving the carriage to the end of its stroke, then moving one bed with respect to the other, again transferring the stitch onto the required needle of the bed from which it had been transferred earlier, then returning the carriage to the end of its stroke, thus returning the displaced bed to the working position, and finally resuming knitting. This operation is rather laborious, entails high mechanical precision in performing the movements of the beds, and requires, for its execution, times which penalize substantially the productivity of the machine.
In two-bed circular knitting machines, the procedure is similar to the one used in rectilinear machines, since the stitch to be transferred is passed from a needle of one bed to a needle of the other bed and is then transferred again to a needle of the bed from which it had been previously transferred after adequately displacing one bed with respect to the other. In this case, in order to displace one bed with respect to the other it is necessary to deactivate the feeds of the machine which must then be reactivated in order to resume knitting. This technique suffers substantially the same problems mentioned above with reference to the method for transferring the stitch on rectilinear machines.
In circular hosiery knitting machines, stitch transfer can be performed by means of two punches arranged laterally, one for each side of the needle, and capable of removing the stitch from the needle, transferring it onto the adjacent needle.
Again in circular hosiery knitting machines, stitch transfer can be performed also by using the hooks of the dial, which lies above the needle cylinder of the machine, as if they were needles of another bed. In both of these cases, the use of elements which are external to the needle limits the gauge that can be reached. Currently, the gauge that can be reached on circular hosiery knitting machines capable of transferring the stitch from one needle to an adjacent needle is 18 n.p.i. (needles per inch).